This invention relates to surgical biopsy needle instruments. More particularly, this invention relates to a coaxial needle for obtaining specimens of solid marrow core biopsy and fluid marrow aspirate in a single procedure.
Known biopsy needles generally include a cannula having a lumen extending therethrough, and a trocar or stylet which is removably inserted through the lumen of the cannula. The proximal ends of the cannula and trocar are provided with some type of gripping means and the distal ends of the cannula and trocar are sharpened to a bone piercing edge. In order to obtain a bone marrow specimen, the trocar and cannula are forced through the outer hard layer of the bone containing the marrow. Once the softer, internal region of the bone is reached, the trocar is withdrawn and a specimen is obtained by advancing the cannula further into the bone. The cannula containing the core sample of bone marrow is then carefully withdrawn so as to retain the marrow material.
The bone marrow biopsy procedure is quite painful to the patient and requires much exertion by the physician. Early problems with biopsy needles involved the sharpness of the cannula and trocar and the gripping means used so that the needle could be placed accurately and the bone could be penetrated quickly. U.S. Pat. No. 4,356,828, for example, discloses an improved finger gripping member and U.S. Pat. No. 4,403,617 discloses particular cutting edge configurations for the trocar and cannula.
Developments in the gripping means of the trocar and cannula continued with emphasis placed on the secure engagement of the trocar within the cannula and ease of use for the physician. U.S. Pat. Nos. 4,922,602; 4,838,282, 4,793,363 and 4,469,109 for example, disclose fairly elaborate interlocking systems between the trocar gripping means and the cannula gripping means and different shapes for the gripping means.
Other problems exist, however, with the known and recently improved biopsy needles. In particular, it is often necessary to obtain two types of specimens of bone marrow: a core sample as described above, and an aspirated sample. To obtain an aspirated sample, the cannula and trocar are inserted under pressure through the outer hard layer of a marrow containing bone. Once the softer, internal region of the bone is reached, the trocar is withdrawn and a specimen is obtained by connecting an aspirating syringe through the proximal end of the cannula and aspirating marrow fluid into the syringe. While both the aspiration and core sample procedures can be performed using the same needle, they do require two separate insertions and despite the improvements in needle sharpness and gripping means design, it is still quite painful to the patient and quite arduous for the physician.
U.S. Pat. No. 5,012,818 to Joishy discloses a "Two in One Bone Marrow Surgical Needle" which comprises an elongated needle with two heads at the proximal end with two portals entering into two parallel hollow lumens leading to two openings at the distal end. One of the lumens is larger and circular and the other is smaller and semilunar. The larger lumen is used to take a core sample specimen and the smaller lumen is used to take an aspirated specimen. While the provided arrangement overcomes the necessity of conducting two procedures to obtain a marrow core and an aspirated sample, it will be appreciated that because the lumens lie parallel to each other, the needle disclosed by Joishy is necessarily large in diameter. Indeed, this is a major drawback of the Joishy needle, as its use is more painful to the patient and requires more effort by the physician.